Why are "unrecoverable" files recoverable?

I just installed Recuva and I must say it is is a powerful tool. But how can it recover files that have been overwritten and marked as unrecoverable? And this is after an Eraser "erase unused space" pass! My concern is that the files I want destroyed are still able to be recovered after a wipe. Can someone please help me with truly deleting my files?

But how can it recover files that have been overwritten and marked as unrecoverable?

For the most part it can't. Two things occuring here 1) file is listed as unrecoverable if you recover it 99.999999% of the time you will get nothing but junk 2)file is still listed in the Master File Table (MFT)

Wikipedia says

The Master File Table (MFT) contains metadata about every file, directory, and metafile on an NTFS volume. It includes filenames, locations, size, and permissions. Its structure supports algorithms which minimize disk fragmentation[citation needed]. A directory entry consists of a filename and a "file ID" which is the record number representing the file in the Master File Table. The file ID also contains a reuse count to detect stale references. While this strongly resembles the W_FID of Files-11, other NTFS structures radically differ.

If you really want too you can wipe the MFT with Wipefreespace on ccleaner

ADVICE FOR USING CCleaner'S REGISTRY INTEGRITY SECTIONDON'T JUST CLEAN EVERYTHING THAT'S CHECKED OFF.Do your Registry Cleaning in small bits (at the very least Check-mark by Check-mark)ALWAYS BACKUP THE ENTRY, YOU NEVER KNOW WHAT YOU'LL BREAK IF YOU DON'T.CCLEANER, RECUVA, DEFRAGGLER AND SPECCY DOCUMENTATION CAN BE FOUND AT www.piriform.com/docsLink to Winapp2.ini explanation

Well, actually it did recover many files that it had marked as "unrecoverable". It did especially well with jpegs, to my surprise. I subsequently reran Eraser with the cluster tips setting and there much fewer files remaining. No files of user note at all, just some 0 byte files and filkes that were locked by Norton, as I ran it within Windows.

Well, actually it did recover many files that it had marked as "unrecoverable". It did especially well with jpegs, to my surprise. I subsequently reran Eraser with the cluster tips setting and there much fewer files remaining. No files of user note at all, just some 0 byte files and filkes that were locked by Norton, as I ran it within Windows.

How did you manage to recover files that were unrecoverable???? did you try it with documents like word, or Open Office? please explain.

Honestly, I don't know. It was my first time using Recuva and I may have done something incorrectly. I also believe that Eraser did not finish properly prior to use, however I did not have any Word docs or other files, just JPEGs and GIFs.